The present invention relates to ink cartridges used for supplying liquid ink to a printhead in a thermal ink jet printing apparatus. Specifically, the present invention relates to structure and methods for filling and venting the ink tank of an ink supply cartridge in a thermal ink jet printing apparatus.
Thermal ink jet printing is well understood in the art. U.S. Pat. No. 5,997,121 describes several aspects of such printing. In existing thermal ink jet printers, the printhead comprises one or more ink filled channels communicating with a relatively small supply chamber, or manifold, at one end, and having an opening at the opposite end, referred to as a nozzle. In current practical embodiments of drop on demand thermal ink jet printers, it has been found that the printers work most effectively when the pressure of the ink in the printhead nozzle is kept within a predetermined range of gauge pressures. Specifically, at those times during operation in which an individual nozzle or an entire printhead is not actively emitting a droplet of ink, it is important that a certain negative pressure, or xe2x80x9cback pressurexe2x80x9d, exist in each of the nozzles and, by extension, within the ink supply manifold of the printhead. The attributes of creating and maintaining such back pressure are described in the U.S. Pat. No. 5,289,212, the contents of which are incorporated herein by reference.
The ink is supplied to the printhead from an ink cartridge. The ink cartridge contains a supply of ink, and is typically configured to maintain the required negative pressure. The ink cartridge is typically a user-replaceable unit that mates with the printhead of the printing apparatus.
In accordance with an aspect of the present invention, a fluid cartridge for supplying fluid on demand includes a wick chamber that has a plurality of outer walls defining an interior that includes a wick chamber. An outlet opening extends through one of the outer walls of the wick chamber, and a vent opening through an outer wall of the wick chamber. The fluid cartridge additionally includes a fluid chamber having a plurality of outer walls, a fluid conduit between the fluid chamber and the wick chamber. The outer walls of the fluid chamber are formed to provide no fluid communication with the fluid chamber except through the wick chamber.
In accordance with another aspect of the present invention, a method of filling a cartridge for supplying liquid ink on demand to an ink jet printhead is provided. The cartridge includes a housing defining a wick chamber and an ink chamber, with a fluid conduit between the ink chamber and the wick chamber. The housing contains wick material in the wick chamber, and has a fluid opening through the housing into the wick chamber. The method of the present invention includes sealing the ink chamber, evacuating gas from the ink chamber and the wick chamber, and supplying ink through the fluid opening into the wick chamber until the ink flows through the fluid conduit into the ink chamber.